Control device for a motor-compressor

ABSTRACT

A control device for motor-compressors in which the working medium is compressed in more than one stage and the power transmitted to the compressor is changed in dependence of the change of the pressure on the delivery side of the compressor above a certain value. The power adjusting mechanism for the motor is actuated in response to a pressure prevailing between two compressor stages to increase the power and in opposite direction for reducing the power by spring means and a control pressure bias on the adjusting mechanism responsive to a pressure change at the delivery side of the compressor so that an increased pressure change reduces the power supply.

United States Patent Berle et al.

[451 Sept. 5, 1972 CONTROL DEVICE FOR A MOTOR- COMPRESSOR Inventors: Axel Gunnar Berle, Antwerp; Lars Gunnar Nilsson, Han Kristoffer Olofsson, both of Wilrijk, all of Belgium Assignee: Atlas Capco Aktiebolog, Macka,

Sweden Filed: July 7, 1970 Appl. No.: 52,942

Foreign Application Priority Data July 17, 1969 Sweden ..10110/69 U.S.Cl. ..417/1s,417/2s,417/34,

Int; Cl. 49/02, F04b 49/08 Field of Search....4l7/28, 1 8, 19, 253, 300, 307,

References Cited UNITED STATES PATENTS 11/1960 Osterkamp ..417/28 5/1961 Dillon ..137/82 Wahl ..417/253 X 2,137,219 11/1938 Aikman ..417/28 2,694,519 11/1954 Paget ..417/28 X 3,043,495 7/ 1962 Hewitt .41 7/28 3,072,319 11/1963 Cox et a1 ...417/28 X- 2,595,369 5/ 1952 Repscha et a] ..417/28 X Primary Examiner-Carlton R. Croyle Assistant Examiner-R. .l. Sher Attorney-Munson'8z Fiddler [57] ABSTRACT A control device for motor-compressors in which the working medium is compressed'in more than one stage and the power transmitted to the compressor is changed in dependence of the change of the pressure on the delivery sideof the compressor above a. certain value. The power adjusting mechanism for the motor is actuated in response to a pressure prevailing between two compressor stages to increase the power and in opposite direction for reducing the power by spring means and a control pressure bias on the adjusting mechanism responsive to a pressure change at the delivery side of the compressor so that an increased pressure change reduces the power supply.

9 Claims, 3 Drawing Figures P'ATENTEDSEP 51912 SHEET 1 OF 3 AXEL GUNNAR BERLE, LARS GUNNAR NILSSON and HANS KRISTOFFER OLOFSSON INVEXTORS M urmszow s. nnnum,

P'ATE'NTEDSEP 5 I972 sum 2 or 3 AXEL GUNHAR BERLE,

LARS GUNNAR NILSSON and HANS KRI'STOFFER. oLoFssou INVENTORS P'IUNSON & FIDDLBR,

Attorneys PATENTEDSEP 5 I972 sum 3 or 3 v Q \Q AXEL GUNNAR BERLE, LARS GUNNAR NILSSON and HANS KRISTOFFER OLOFSS X INVENT S I 'IIUHIJUH- i. ["IDULI'ZH,

CONTROL DEVICE FOR A MOTOR-COMPRESSOR This invention relates to a control device for motorcompressors in which the working medium is compressed in more than one stage and the power transmitted to the compressor is changed in dependence of the change of the pressure at the delivery side of the compressor above a certain value. One object of the invention is to produce an improved control device in which the power taken from the motor is adjusted within wide limits in proportion to the power necessary for driving the compressor. A further object of the invention is to provide a control device which is comparatively simple and which utilizes pressure fluid available within the compressor for operation of the control device. A further object of the invention is to provide a device which is more efficient than known devices for controlling motor-compressor units. v

In the accompanying drawings one embodiment of a control device according to the invention and adapted for a two stage motor-compressor is illustrated by way of example.

FIG.'1 is a diagrammatic view of a motor-compressor according to the invention illustrating the control device and the various necessary connections in a two stage motor-compressor unit according to the inventron.

FIGS. 20 and 2b are detail views partly in section of the most important details of the control device according to FIG. 1. v

The motor-compressor unit diagrammatically illustrated in FIG. 1 consists of a motor 1, which may, for instance, be a diesel engine provided with a fuel supply mechanism 2 such as a fuel injection pump, in which the quantity of fuel delivered to the motor may be increased or reduced by swinging a fuel control arm 3 between a stop 4 and a stop 5 which represent the maximum power position of the motor and the idling position of the motor, respectively. The motor 1 is coupled to the compressor by means of a transmission 6. The two stage compressor comprises a low pressure compressor 7 and a high pressure compressor 8 which are driven from the transmission 6 over suitable gears (not illustrated) disposed in a transmission casing 9. The compressors 7,8 may, for instance, be screw compressors. The low pressure compressor 7 has a suction conduit 10 provided with an intake filter 11 and a throttle valve 12 which may be adjusted from the diagrammatically illustrated throttling position in FIG. 1 to an open position by means of a slidable control rod 13. From the low pressure compressor 7 the compressed working medium flows through a conduit 14 to an intermediate cooler 15 and further through a conduit 16 to the high pressure compressor 8 from which the compressed working medium via a check valve 17 and a conduit 18 flows to an after-cooler 19 and from there to a receiver 20 from which a compressed air network 21 is fed over a valve 22.

The motor-compressor unit is provided with a lubricating oil pump 23 from which among others a conduit 24 leads to a slide valve housing 25 in which a piston slide valve 26 is movable under the action of a spring 27 and a push button 28 which is manually operated. From the valve housing 25 oil is conducted through a conduit 29 to a chamber 30 in a valve housing 31 of an operating valve 32 serving to load and unload the compressor.

The operation of the compressor unit is controlled by members on the control rod 13 which is coupled to the throttle valve 12 in the intake conduit of the compressor unit and which at one end is provided with an operating piston 33 which is movable in an operating cylinder 34 against the action of a spring 35 from the position illustrated in FIG. 1 in which the throttle valve throttles the air supply to the compressor 7 through the intake-conduit 10 to open position of the throttle valve 12 in which position a valve member 36 provided on the control rod closes an air-venting conduit 37 communicating with the delivery side of the high'pressure compressor 8. The conduit 37 is connected at the compressor side of the check valve 17. v

40 indicates a power control mechanism which is illustrated in detail in section in FIG. 2b and consists of an operating cylinder 41 in which a piston 42 carried on the end of a fuel control rod 43 is displaceable-from the illustrated idling position to a position representing full power supply to the motor in which position the arm 3 abuts the stop 4.' The piston 42 is actuated in the direction towards the idling position by a spring 44 and in opposite direction by pressure fluid in a chamber 45 in the cylinder 41. Said chamber is fed with compressed air from the conduit 14 extending between the low pressure stage and the high pressure stage of the compressor. A supply conduit 46 connects the conduit 14 with the chamber 45.

At the other side of the piston 42 in the cylinder 41 a chamber 47 is formed which through a conduit 48 communicates with a pressure converter or pressure amplifier 49, FIG. 2a, which through a conduit 50 communicates with the receiver 20 and is fed with pressure medium from said receiver. The pressure converter 49 contains a chamber 51 which communicates with the conduit 50 via a filter 52 and passages 53 in the pressure converter housing. The pressure converter also contains a chamber 54 and a chamber 55 communicating with the atmosphere in which a helical spring 56 is disposed. The chambers 51 and 54 are separated by a diaphragm 57 having a hub portion 58 which carries a ball valve 59 which in FIG. 2a is illustrated in a position in which it closes a passage 60 forming a communication between the chamber 51 and the chamber 54. The chambers 54 and 55 are separated by a diaphragm 61 and the relation between the operative areas of the diaphragms 57 and 61 is such that substantially twice the pressure is necessary in the chamber 54 in order to balance the pressure in the chamber 51. The tension of the spring 56 may be adjusted by means of a screw 62, and said spring substantially balances the receiver pressure in the chamber 51 and may, for instance, be adjusted in such a way that the valve 59 is kept closed when the receiver pressure is 7 atmospheres above atmospheric pressure. If the pressure in the chamber 51 rises, for instance to 7.1 atmospheres above atmospheric pressure then the valve 59 lifts from its seat and compressed air flows into the passage 60 to the chamber 54. When the pressure in said chamber has reached 0.2 Kg/cm equilibrium is obtained between the pressures in the chambers 51 and 54. The control pressure 0.2 Kg/cm obtained in the passage 60 is consequently in this case twice the change 0.1 Kg/cm in the receiver pressure.

The control pressure in the passage 60 is supplied to an unloading valve housing 63 which contains a first chamber 64 and a second chamber 65 and a diaphragm 66 which is biased downwards in FIG. 2a by the pressure in the chamber 64 and a spring 67 provided in the housing. The unloading valve housing 63 furthermore contains a shift valve 68. The shift valve 68 has two valve members 69 and 70 which cooperate with seats 71 and 72, respectively, in the housing 63. The housing 63 has an inlet passage 73, which connects the passage 60 with the chamber 64, and an inlet passage 74, which connects the passage 53 in the housing 49 with a bore 75 in the housing 63. Said bore contains the valve member 70 and a spring 76 acting on said valve member. The tension of the spring 76 is adjustable by a suitable choice of a number of shims 96. The housing 63 has an outlet passage 77 which forms a constant communication between the chamber 65 and the atmosphere. The housing 63 has a further outlet passage 78 which communicates with aconduit 79 leading to the operating valve housing 31, FIG.-1, and a chamber 80 provided therein. In the illustrated position of the shift valve 68 the outlet passage 78 is vented to the atmosphere through the chamber 65 and the outlet passage 77. The diaphragm 66 is resilient and has a spring force directed upwards in FIG. 2a and counteracting the pressure in the chamber 64 and the spring force of the helical spring 67 which may be adjusted by a screw 81. .When the pressure in the chamber 64 and the force of the spring 67 overtake the spring force of the diaphragm 66 then said diaphragm snaps over to a downwardly deflected position in which it displaces the valve member 68 so that the valve member 69 interrupts the venting from the passage 78 to the passage 77 Simultaneously, the valve member 70 admits control or operating air from the receiver through the passage 78 and the conduit 79 to the chamber 80.

From the supply conduit 46, FIG. 1, which communicates with the intermediate cooler 15 a conduit 83 leads to a housing 84 in which a diaphragm or flapper valve 85 is disposed. Said valve is a shift valve, which in the illustrated position provides a communication between a conduit 86 and a vent passage 87. The conduit 86 communicates with a chamber 88 at one side of the diaphragm or flapper valve 85. The valve 85 has an opening 89 and, when the pressure in the conduit 83 moves the valve member to the left hand position in FIG. 1, then the vent passage 87 is closed and a communication is opened between the conduit 83 and the conduit 86 through the opening 89.

The operating valve housing 31 contains two diaphragms 90 and 91 and chambers 92 and 93.

The control device according to the invention illustrated in FIGS. 1, 2a and 2b operates in the following manner:

The motor compressor unit is illustrated in FIG. 1 with the fuel control arm 3 in the idling position and with the compressor unloaded and running idle. The control rod 13 keeps the valve member 36 open so that the high pressure stage 8 of the compressor communicates with the atmosphere through the conduit 37. In the intermediate cooler atmospheric pressure also prevails since the intermediate cooler is vented through the high pressure stage. The shift valve 85 is in the position illustrated in FIG. 1. The operating valve 32 is similarly in the position illustrated in FIG. 1 and the conduits 95,94 are vented to the atmosphere through the cylinder 34 and a conduit 97 communicating with the suction side of the compressor. The diaphragm 66 in the unloading valve 63 is deflected downwards and g the passage 74 communicates with the passage 78 over the open valve member 70. The reloading push button 28'is pressed inwards and pressure oil from the pump 23 acts on the diaphragm in the chamber 30. The receiver pressure in 20, which via 50,74,78 and 79 acts in the chamber 80, is higher than the oil pressure in 30 so that the compressor runs unloaded.

When the motor and compressor are at stand still with pressure in thereceiver 20 the various parts of the plant take the positions illustrated in the figures with the exception that the spring 27 keeps the push button 28 moved towards the left in FIG. 1 so that 26 interrupts the communication between 24 and 29. When it is desired to load the compressor after it has been at rest with pressure in the receiver-the following operation is carried out:

When the motor has been started and run warm the push button 28 is pressed to the position'illustrated in FIG. 1 in which the piston slide valve 26 admits pressure oil from the oil pump of the compressor through the conduit 24 to the conduit 29 and the chamber 30 at the under side of the diaphragm 90. Said diaphragm is then deflected upwards and the valve member 32 is moved upwards so that the valve member 98 is lifted from its seat and the valve member 99 closes the communication between the conduit 94 and 95. The vacuum in the suction conduit 10 then actuates the operating piston 33 so that the compressor starts working anda soon as pressure has been built up in the intermediate cooler the shift valve 85 snaps over from the illustrated position to the left hand position in FIG. 1 and admits intermediate cooler pressure through the conduit 86, the chamber 93 and the conduit to the chamber 100 in the operating cylinder 34 so that the throttle valve 12 is completely opened and the valve 36 closes the vent passage from the high pressure stage 8 of the compressor. The compressor now runs fully loaded and the motor operates with full fuel supply since the intermediate cooler pressure in the chamber 45 presses the piston 42 all the way towards the right in FIG. 2b.

If the air consumption from the receiver 20 is less than the delivery of the compressor then the pressure in the receiver rises and when said pressure has exceeded a certain value, for instance 7 atmospheres above at-. mospheric pressure, then the power control mechanism 40 starts to function. This is due to the fact that control air from the conduit 60 flows through the conduit 48 to the chamber 47 in the cylinder 41 and moves the piston 42 towards the left in FIG. 2b and thereby reduces the fuel supply to the motor. This occurs gradually as the control'pressure in the passage 60 rises until finally the piston 42 reaches bottom position, as illustrated in FIG. 2b, and the motor has been slowed down to idling position. Now, if the pressure in the receiver should start to sink due to an increased air consumption then the control pressure in the conduit 60 is reduced and the piston 42 moves towards the right in FIG. 2b so that the power control mechanism for the motor is adjusted for increased fuel supply. From the cylinder 41 a restricted passage 101 leads to the atmosphere and said passage I serves to vent the cylinder 41, the pressure converter 49 and the chamber 64 when the compressor plant is at stand still.

The power control mechanism 40 is arranged in such a manner that it depends on the existance of working medium pressure in the intermediate cooler between the compressor stages 7 and 8. Beforev such pressure has been built up the motor can not be driven with full power.

The control device above described and illustrated on the drawings and the various details thereof should only be considered as examples and may be modified in various different ways within the scope of the following claims.

We claim:

1. A control assembly for a motor and compressor in which the working medium is progressively compressed in a plurality of stages and the power output transmitted from the motor to the compressor is varied in dependence of a change above a predetermined value of the outlet medium pressure at the delivery side of the compressor, said control assembly comprising:

a. a power control mechanism adapted to control the input power to the motor,

b. said power control mechanism including an adjusting means for actuating said control mechanism in response to an interstage pressure of the compressor,

c. a pressure converter arranged to amplify the pressure medium increase above the predetermined value at the delivery side of the compressor to provide a control pressure which is a multiple of said pressure increase, and

d. said pressure converter being connected to said adjusting means for countering said interstage pressure with the control pressure so that the power input to said motor is reduced in response to an increase of the control pressure.

2. A control assembly as defined in claim 1 wherein said adjusting means includes a spring means arranged to aid said control pressure in countering said interstage pressure.

3. A control assembly as defined in claim 1 which includes an unloading mechanism adapted to be connected to the delivery side of said compressor for relieving the outlet medium pressure, and

a control valve operatively connected to said unloading mechanism and responsive to said control pressure whereby said unloading mechanism is actuated to relieve the outlet medium pressure from said delivery side of said compressor when the control pressure reaches a certain value.

4. A control assembly for a motor-compressor in which the working medium is progressively compressed in a plurality of stages and the motor drive power to the compressor is varied in dependence upon a pressure change above a predetermined value of the outlet medium pressure at the delivery side of the compressor, said control assembly comprising:

a. a power control means adapted to change the input power to the motor so as to vary the motor drive power to the compressor,

b. said power control means including adjusting means for actuating said power control means responsive to an interstage pressure of the compressor, and

spring means disposed to counter said interstage pressure on said adjusting means,

c. pressure sensing means for sensing the outlet medium pressure and providing a control pressure to the adjusting means when said outlet medium pressure exceeds said predetermined value,

d. said adjusting means being responsive to said control pressure to aid said spring means in countering the interstage pressure whereby the input power to said motor is reduced in response to an increase in the output medium pressure from said compressor.

5. A control assembly as defined in claim 4 wherein said pressure sensing means includes a converter means for amplifying an increase in the outlet medium pressure above the predetermined value whereby the control pressure is a multiple of said pressure increase.

6. A control assembly as defined in claim 4 which includes an unloading mechanism adapted to be connected to the delivery side of said compressor for relieving the outlet medium pressure, and

a control valve operatively connected to said unloading mechanism and responsive to said control pressure whereby said unloading mechanism is actuated to relieve the outlet medium pressure from said delivery side of said compressor when the control pressure reaches a certain value.

7. A control assembly as defined in claim 4 wherein said control pressure is proportional to the change in the outlet medium pressure above the predetermined value of the outlet medium pressure at the delivery side of the compressor, and

said pressure sensing means includes a spring biasing means which is adapted to define the predetermined value of the outlet medium pressure and a tension adjusting means for said spring biasing means whereby the predetermined value may be adjusted.

8. A control assembly as defined in claim 4 wherein said adjusting means includes a pressure fluid cylinder,

a piston and piston rod slidably mounted in said cylinder,

connecting means adapted for connecting said piston rod to the motor whereby the input power to said motor may be varied by movement of said piston rod,

said pressure fluid cylinder including a first chamber at one side of the piston subjected to said control pressure and a second chamber in the cylinder at the opposite side of the piston subjected to an interstage pressure of the compressor whereby said interstage pressure moves said piston in a direction so as to increase the power input to said motor.

9. A control assembly as defined in claim 4 wherein said adjusting means includes a pressure cylinder,

a piston and piston rod slidably mounted in said pressure cylinder, and

connecting means adapted for connecting said piston rod to the motor whereby the motor input power may be varied by movement of said piston rod, and

said pressure sensing means includes a pressure converter and a conduit connecting said pressure converter with said pressure cylinder whereby the control pressure causes the piston and piston rod to reduce the input power to said motor in response to an increase in the control pressure and said pressure converter including two chambers separated by a pressure diaphragm, a valve 

1. A control assembly for a motor and compressor in which the working medium is progressively compressed in a plurality of stages and the power output transmitted from the motor to the compressor is varied in dependence of a change above a predetermined value of the outlet medium Pressure at the delivery side of the compressor, said control assembly comprising: a. a power control mechanism adapted to control the input power to the motor, b. said power control mechanism including an adjusting means for actuating said control mechanism in response to an interstage pressure of the compressor, c. a pressure converter arranged to amplify the pressure medium increase above the predetermined value at the delivery side of the compressor to provide a control pressure which is a multiple of said pressure increase, and d. said pressure converter being connected to said adjusting means for countering said interstage pressure with the control pressure so that the power input to said motor is reduced in response to an increase of the control pressure.
 2. A control assembly as defined in claim 1 wherein said adjusting means includes a spring means arranged to aid said control pressure in countering said interstage pressure.
 3. A control assembly as defined in claim 1 which includes an unloading mechanism adapted to be connected to the delivery side of said compressor for relieving the outlet medium pressure, and a control valve operatively connected to said unloading mechanism and responsive to said control pressure whereby said unloading mechanism is actuated to relieve the outlet medium pressure from said delivery side of said compressor when the control pressure reaches a certain value.
 4. A control assembly for a motor-compressor in which the working medium is progressively compressed in a plurality of stages and the motor drive power to the compressor is varied in dependence upon a pressure change above a predetermined value of the outlet medium pressure at the delivery side of the compressor, said control assembly comprising: a. a power control means adapted to change the input power to the motor so as to vary the motor drive power to the compressor, b. said power control means including adjusting means for actuating said power control means responsive to an interstage pressure of the compressor, and spring means disposed to counter said interstage pressure on said adjusting means, c. pressure sensing means for sensing the outlet medium pressure and providing a control pressure to the adjusting means when said outlet medium pressure exceeds said predetermined value, d. said adjusting means being responsive to said control pressure to aid said spring means in countering the interstage pressure whereby the input power to said motor is reduced in response to an increase in the output medium pressure from said compressor.
 5. A control assembly as defined in claim 4 wherein said pressure sensing means includes a converter means for amplifying an increase in the outlet medium pressure above the predetermined value whereby the control pressure is a multiple of said pressure increase.
 6. A control assembly as defined in claim 4 which includes an unloading mechanism adapted to be connected to the delivery side of said compressor for relieving the outlet medium pressure, and a control valve operatively connected to said unloading mechanism and responsive to said control pressure whereby said unloading mechanism is actuated to relieve the outlet medium pressure from said delivery side of said compressor when the control pressure reaches a certain value.
 7. A control assembly as defined in claim 4 wherein said control pressure is proportional to the change in the outlet medium pressure above the predetermined value of the outlet medium pressure at the delivery side of the compressor, and said pressure sensing means includes a spring biasing means which is adapted to define the predetermined value of the outlet medium pressure and a tension adjusting means for said spring biasing means whereby the predetermined value may be adjusted.
 8. A control assembly as defined in claim 4 wherein said adjusting means includes a pressure fluid cylinder, a piston and piston rod slidably mounted in said cylinder, connecting means adapted for connecting said piston rod to the motor whereby the input power to said motor may be varied by movement of said piston rod, said pressure fluid cylinder including a first chamber at one side of the piston subjected to said control pressure and a second chamber in the cylinder at the opposite side of the piston subjected to an interstage pressure of the compressor whereby said interstage pressure moves said piston in a direction so as to increase the power input to said motor.
 9. A control assembly as defined in claim 4 wherein said adjusting means includes a pressure cylinder, a piston and piston rod slidably mounted in said pressure cylinder, and connecting means adapted for connecting said piston rod to the motor whereby the motor input power may be varied by movement of said piston rod, and said pressure sensing means includes a pressure converter and a conduit connecting said pressure converter with said pressure cylinder whereby the control pressure causes the piston and piston rod to reduce the input power to said motor in response to an increase in the control pressure, and said pressure converter including two chambers separated by a pressure diaphragm, a valve member connected to said diaphragm and arranged so that when one one of said diaphragm chambers is connected to the output medium pressure at the delivery side of the compressor, the valve member is moved in an opening direction and when control pressure is applied to the opposite diaphragm chamber, said valve member is actuated in a closing direction. 